The upcoming revision of the International Classification of Diseases (ICD)-11 will provide the first comprehensive diagnostic scheme for chronic pain on the basis of biopsychosocial definition of chronic pain. This new classification scheme comprises 7 diagnostic categories. In light of these changes, the International Association for the Study of Pain Task Force answered future ICD-11 users’ frequently asked questions which were published in the journal Pain.

The ICD-11 went into effect for worldwide statistical mortality reporting January 1, 2022, and each country will decide when to implement these guidelines for routine clinical practice.

There are 2 versions of the ICD-11, an orange and a blue version. These versions are an attempt to simplify ICD-11’s complex structure, which comprises >120,000 terms. The blue version contains short descriptions of each entry and was ‘frozen’ at a specific time such that it remains an unchanged reference guide. The orange version is the ‘ICD-11 Maintenance Platform’ and contains complete information and continues to be updated.


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The new pain classification system is intended for all patients including pediatric patients and those with intellectual or other disabilities and the nonverbal populations.

The new diagnostic categories of chronic pain include:

·   MG30.0 Chronic primary pain

·   MG30.1 Chronic cancer-related pain

·   MG30.2 Chronic postsurgical or post traumatic pain

·   MG30.3 Chronic secondary musculoskeletal pain

·   MG30.4 Chronic secondary visceral pain

·   MG30.5 Chronic neuropathic pain

·   MG30.6 Chronic secondary headache or orofacial pain

An additional digit is added to each category for specific area subcategories, for instance adding a 2 to MG30.3 is the diagnostic category for MG30.32 Chronic secondary musculoskeletal pain due to disease of the nervous system.

There are extension codes which can be coded alongside the plain classifiers. These extension codes are based on the numerical rating scale (NRS), in which the patient ranks their pain intensity, pain-related distress, and pain-related interference on an NRS of 0 (no pain/distress/interference) to 10 (worst/extreme pain or unable to function). These scores are transformed into mild (NRS, 1-3), moderate (NRS, 4-6), and severe (NRS, 7-10) classifications.

Clinicians should be aware that not all ICD-11 diagnoses can be found in the blue ICD-11. For example, the ICD-11 diagnosis of Chronic primary low back pain will now be designated as MG30.02 Chronic primary musculoskeletal pain.

To facilitate an easy transition to the new classification process, a binary decision tree has been developed as an algorithm for clinicians to follow during clinical practice.

Clinicians who participated in studies of these new classifiers for chronic pain indicated that the utility of these diagnoses was very high, and they thought these classifications would improve communication with patients and colleagues. This classification scheme fulfils both long-term demands from the pain community and has incorporated novel aspects based on the biopsychosocial model of chronic pain.

As new evidence regarding chronic pain diagnoses becomes available, these updates will be made available in the ICD-11 orange version.

Reference

Korwisi B, Barke A, Rief W, Treede R-D, Kleinstäuber M. Chronic pain in the 11th revision of the International Classification of Diseases: users’ questions answered. Pain. Published online December 3, 2021. doi:10.1097/j.pain.0000000000002551